1. Field of the Invention
This invention relates to a semiconductor wafer and a semiconductor device manufacturing method with which it is possible to prevent to the utmost the occurrence of residues such as black silicon when forming a trench for isolation/separation or for capacitor formation in a semiconductor substrate such as a silicon substrate by dry etching process.
2. Description of the Related Art
Forming trenches for device separation in a semiconductor wafer, for example a silicon wafer, has been proposed in, for example, Japanese patent application laid-open No. H.5-109882. In forming a trench, an oxide film is formed on the wafer surface by a CVD method or the like, and an opening is formed in this oxide film by photolithography process over a trench formation region. That is, the oxide film is used as an etching mask. Silicon of the trench formation region exposed by the opening in the oxide film is then selectively etched by reactive ion etching (RIE) process or the like to form a trench of, for example, about 10 to 15 .mu.m in depth.